<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- This file documents the BFD library.

Copyright (C) 1991-2020 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding
Free Software", the Front-Cover texts being (a) (see below), and with
the Back-Cover Texts being (b) (see below).  A copy of the license is
included in the section entitled "GNU Free Documentation License".

(a) The FSF's Front-Cover Text is:

A GNU Manual

(b) The FSF's Back-Cover Text is:

You have freedom to copy and modify this GNU Manual, like GNU
     software.  Copies published by the Free Software Foundation raise
     funds for GNU development. -->
<!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Creating a Linker Hash Table (Untitled Document)</title>

<meta name="description" content="Creating a Linker Hash Table (Untitled Document)">
<meta name="keywords" content="Creating a Linker Hash Table (Untitled Document)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<link href="index.html#Top" rel="start" title="Top">
<link href="BFD-Index.html#BFD-Index" rel="index" title="BFD Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Linker-Functions.html#Linker-Functions" rel="up" title="Linker Functions">
<link href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" rel="next" title="Adding Symbols to the Hash Table">
<link href="Linker-Functions.html#Linker-Functions" rel="prev" title="Linker Functions">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smalllisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<a name="Creating-a-Linker-Hash-Table"></a>
<div class="header">
<p>
Next: <a href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" accesskey="n" rel="next">Adding Symbols to the Hash Table</a>, Previous: <a href="Linker-Functions.html#Linker-Functions" accesskey="p" rel="prev">Linker Functions</a>, Up: <a href="Linker-Functions.html#Linker-Functions" accesskey="u" rel="up">Linker Functions</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Creating-a-linker-hash-table"></a>
<h4 class="subsection">2.17.1 Creating a linker hash table</h4>
<a name="index-_005fbfd_005flink_005fhash_005ftable_005fcreate-in-target-vector"></a>
<a name="index-target-vector-_0028_005fbfd_005flink_005fhash_005ftable_005fcreate_0029"></a>
<p>The linker routines must create a hash table, which must be
derived from <code>struct bfd_link_hash_table</code> described in
<code>bfdlink.c</code>.  See <a href="Hash-Tables.html#Hash-Tables">Hash Tables</a>, for information on how to
create a derived hash table.  This entry point is called using
the target vector of the linker output file.
</p>
<p>The <code>_bfd_link_hash_table_create</code> entry point must allocate
and initialize an instance of the desired hash table.  If the
back end does not require any additional information to be
stored with the entries in the hash table, the entry point may
simply create a <code>struct bfd_link_hash_table</code>.  Most likely,
however, some additional information will be needed.
</p>
<p>For example, with each entry in the hash table the a.out
linker keeps the index the symbol has in the final output file
(this index number is used so that when doing a relocatable
link the symbol index used in the output file can be quickly
filled in when copying over a reloc).  The a.out linker code
defines the required structures and functions for a hash table
derived from <code>struct bfd_link_hash_table</code>.  The a.out linker
hash table is created by the function
<code>NAME(aout,link_hash_table_create)</code>; it simply allocates
space for the hash table, initializes it, and returns a
pointer to it.
</p>
<p>When writing the linker routines for a new back end, you will
generally not know exactly which fields will be required until
you have finished.  You should simply create a new hash table
which defines no additional fields, and then simply add fields
as they become necessary.
</p>
<hr>
<div class="header">
<p>
Next: <a href="Adding-Symbols-to-the-Hash-Table.html#Adding-Symbols-to-the-Hash-Table" accesskey="n" rel="next">Adding Symbols to the Hash Table</a>, Previous: <a href="Linker-Functions.html#Linker-Functions" accesskey="p" rel="prev">Linker Functions</a>, Up: <a href="Linker-Functions.html#Linker-Functions" accesskey="u" rel="up">Linker Functions</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-Index" title="Index" rel="index">Index</a>]</p>
</div>



</body>
</html>
